The Slug was a large obese deformed creature who lived in the sewers of Gotham City. He is a giant albino with some degree of intelligence. Underground in the sewers, Slug gathered homeless and run away teenagers. As Outsiders, he lectured them on the decay of society and used three particular agents as enforcers. They routinely destroyed shopping malls until they were actively pursued by Batman.

After a week, Batman was able to discover a bidden stairwell to Slug's inner sanctum. It also turned out that he utilized nearby abandoned toxic waste to mutate turtles into behemoths. In a one-on-one fight, Slug was easily defeated by Wildcat. Wildcat tossed Slug into a river of toxic waste. Slug further mutated and grew larger, tentacles, and could generate acid spit. Black Lightning, Katana, and Metamorpho were reasoned with and defeated Slug.